A centrifugal microfluidic emulsifier integrated with oil storage structures for robust digital LAMP.

Centrifugal droplet-based microfluidic devices have been applied to biomedical analysis and diagnostics recently. However, in centrifugal droplet-based microfluidic devices, droplets are tightly packed (i.e., the oil film between neighbouring droplets is thin). Therefore, droplet coalescence usually occurs especially during thermal incubation process. To preserve individual droplets in the devices, we report a new design for monodisperse droplet generation and storage that exploits a centrifugal configuration for droplet emulsification and oil-storage structures (OSSs) for regulation of the thickness of oil film between neighbouring droplets. The centrifugal emulsifier was well designed to ensure uniform droplet generation. Meanwhile, the OSSs could store oil during centrifugal emulsification while release oil before thermal incubation, which "loosen" tightly packed droplets to prevent droplets from coalescing. In this paper, the working process of OSS was analysed, and its shape and size were optimized. Then, the optimized OSSs were integrated into a centrifugal emulsifier for droplet digital loop mediated isothermal amplification (ddLAMP) by which detection of JAK2 V617F mutation within myeloproliferative neoplasms with a dynamic range of 10 to 10 copies per μL was achieved. We anticipate that the simplicity and robustness of our system make it attractive as an inexpensive and easy-to-operate device for DNA amplification, particularly applicable in point-of-care settings.